1. Field of the Invention
The present invention relates to a multifunction system, and more particularly to a multifunction system in which plural functions including an image output function can be used in an identical system.
2. Description of the Prior Art
Recently, there is known a multifunction system in which plural functions such as a copy function, a scanner function, a printer function, and a facsimile function can be used in one apparatus or one system by handling image information as digital signals.
FIG. 13 shows a conceptual diagram of such a multifunction system. In the drawing, an image input terminal (IIT) 100 corresponds to an original reading device; an image output terminal (IOT) 102 corresponds to a printer; and a controller 104 includes an interface for sending and receiving image signals to and from external networks such as the Internet, interfaces with the IIT 100 and the IOT 102, and a storage device (not shown) for storing image information.
The controller 104, which controls system operations such as a print instruction and a scan instruction, has a network interface and a modem to enable data input and output with the outside world, The devices are connected with each other by wiring the number of lines corresponding to the number of bits of an image signal, and are electrically connected with each other by switching signal switching units S1, S2, and S3 provided in wiring paths according to a desired function.
Because of this construction, if a new functional unit is added, an additional switch is required to switch the connections among the functional units, with the result that not only the device configuration becomes complicated but also the wiring must be redesigned.
A recent trend has been toward more and more wired lines because of an increase in the data quantity of image signal attendant on higher image quality. For example, the connection between the IIT 100 and the controller 104 would require plural signal lines for sending pixel data and plural control lines for controlling a printer, so that as many signal lines as the signals would be required, one signal line for each signal. For example, for image data only, a monochromatic printer would require N signal lines to send and receive information of one pixel in N bits, and a color printer would require M by N signal lines when the number of colors per pixel is M.
To solve the above-described problems, there is currently an attempt to increase operation speed and restrain device size by pushing ahead with a parallelism approach by multilayering and miniaturizing connection lines. However, there is a problem in that system processing speed is limited by the transmission speed of parallel signals due to signal delay caused by the capacity between connection wirings and connection wiring resistance. Also, the problem of electromagnetic interference (EMI) caused by highly dense connection wiring greatly impedes an increase in system processing speed.
As the technology for decreasing the number of signal lines, the technology for sending plural types of image data in time division is disclosed in Japanese Published Unexamined Patent Application No. Hei 7-25079. This technology reduces communication speed and cannot fundamentally solve the complexity of inter-device connections.
With improvement in CPU, communication speed, and processing speed of storage devices, there is an increasing demand for the ability to execute the so-called concurrent job of concurrently performing plural functions, e.g., a print function and a scanner function.
However, more complicated device configuration is required to execute concurrent jobs in a multifunction system that employs electric wiring.
In this regard, a description is made with reference to FIG. 13 described previously. Since a copy job (the operation of outputting an image obtained from the IIT 100 from the IOT 102) and a print job (the operation of outputting image information stored in advance in the controller 104 from the IOT 102) are sent to the same image output device (IOT) 102, the operations are controlled so that no event occurs at the same time.
Accordingly, if it is assumed that, e.g., a print job and a scan job (the operation of storing an image obtained from the IIT 100 in a memory of the controller 104) that may be transmitted at the same time are executed at the same time, they must take different paths from each other, as shown in the dotted lines in the drawing.
To send and receive image signals associated with the respective jobs by using an identical path without changes, with the respective jobs divided in time series, they have to be processed while adjusting timing. However, where processing is performed in the time division mode, the processing cannot be rapidly performed because two jobs are processed through synchronous transmission to and from the IOT 102.
Accordingly, using the signal line switching parts S1, S2, and S3, respective wirings may be separated from each other so that they can be used independently. The signal switching parts turn on or off signal transmission according to the jobs. For the copy job, the signal switching unit S1 is turned on, and the signal switching parts S2 and S3 are turned off. For the scan job, the signal switching part S2 is turned on, and the signal switching parts S1 and S3 are turned off. For the print job, the signal switching part S3 is turned on, and the signal switching parts S1 and S2 are turned off. The scan job and the print job can be executed at the same time by turning on the signal switching parts S2 and S3 and turning off the signal switching part S1.
However, this method has a problem in that the signal switching parts must be controlled for each job, and an increase in the number of wirings expands a mounting area.
In recent years, there has been a demand to share as many types of equipment handling digital signals as possible to save office space, so that more functional units tend to be added.
FIG. 14 shows a system in which a FAX controller 106 is provided in addition to the controller 104 of FIG. 13. Where plural controllers are installed in the system, it is apparent that the system becomes complicated as shown in FIG. 14. The FAX controller 106 herein includes a modem (not shown) connected to a telephone line to control PAX transmission, sends images sensed by the IIT 100 by a FAX function, and outputs images received by the FAX function to the IOT 102.
As has been described above, since the functional units are connected using electric wirings in the multifunction system, it is difficult to build a high-speed and expandable system.
As shown in FIG. 15, to reduce EMI and signal delay, a method of replacing electric wirings by optical fibers 108 is conceivable. However, although mere speedup of transmission speed can be achieved, there is no substantial change from the case of electric wirings, so that the complexity of wirings and poor expandability cannot be solved.
Where different jobs are to be executed at the same time in a multifunction system, a system using electric wirings as common signal paths has been afflicted with not only complicated wiring placement but also complicated control of plural signal switching parts, as well as an increase in the number of wirings caused by an increase in the number of bits and larger capacity of processors and image signals, placing a strong constraint on device design.